Sheriff Jones said some homes had been reduced to slabs. Authorities fear the death toll could rise.

Local resident Scott Fillmer said: "Everything just kind of went dark, when it was almost like night outside. And it's that old cliché that it sounds like a freight train coming, well that's what it sounded like."

Residents of Smiths Station told local TV they had seen businesses destroyed there. A large bar called the Buck Wild Saloon had had its roof torn off.

Image copyrightScott FillmerImage caption
Beauregard was one of the worst hit areas

Image copyrightAFP/Justin Merritt via InstagramImage caption
A tornado as seen in Dothan in Alabama on Sunday

Sheriff Jones said: "The challenge is the sheer volume of the debris where all the homes were located. It's the most I've seen that I can recall."

Tornado warnings were also issued for Georgia, Florida and South Carolina. Footage showed smashed buildings and snapped trees in Talbotton, about 80 miles south of Atlanta.

Tornadoes were also reported in Walton County and Cairo in northern Florida.

What do we know about the casualties?

All of the deaths so far have been in Lee County. Authorities say they are still working to identify the victims and the injured.

One of the dead in Beauregard was an eight year old, family members said.

Are tornadoes expected at this time of year?

This series has occurred earlier than the traditional peak season for tornadoes, which runs from April to June, when more than half of the year's tornadoes generally strike.

Weather systems are more conducive in these months. Warm air flows north from the Gulf of Mexico at the same time as storm systems are propelled into the south and mid-west by a southward dip in the jet stream.

These latest tornadoes appear to have carried the deadliest toll since 35 people were killed in Arkansas and Mississippi in April 2014.

A "super outbreak" of tornadoes across a swathe of the US in April 2011 killed more than 300 people.